This application claims the priority of Korean Patent Application No. 2002-41798, filed Jul. 16, 2002 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1 Field of the Invention
The present invention relates to a method and apparatus for encoding and decoding motion vectors. More specifically, the present invention relates to a method and apparatus for encoding and decoding motion vectors calculated with reference to a plurality of pictures.
2 Description of the Related Art
According to MPEG-1 or MPEG-2 coding standards, P-picture coding that refers to a previous picture or B-picture coding that refers to both previous and following pictures is adapted to encode a present picture, and motion compensation is carried out on the basis of the coding type. Further, in order to improve coding efficiency, prediction coding is carried out using motion vectors of neighbor blocks so that the relationship between the motion vectors of the neighbor blocks can be reflected, rather than directly coding the motion vector of the present block itself.
Occasionally, the motion vectors of the neighbor blocks used in the prediction coding may not refer to the same reference picture as that which refers to the motion vector of the present block. If such an occasion arises, it is conventional to exclude the motion vectors of the neighbor blocks referring to a different reference picture from the prediction coding process, because the coding efficiency can be lowered in the event that the motion vectors obtained on the basis of the different reference picture are use in the prediction coding. However, in the case of excluding the motion vectors of the neighbor blocks referring to the different reference picture from the prediction coding process, the relationship between the motion vectors of the neighbor blocks is not sufficiently reflected and, therefore, the coding efficiency of the motion vectors can be correspondingly lowered. The problem is much more serious in the case of pictures including more such blocks that refer to different reference pictures.